With a more complex color palette than the previous black (or gray) on white default themes, we will have to check contrast ratios more carefully, with a goal of 4.5:1 for body text, and 3:1 for large text, as recommended by WCAG 2.0 accessibility guidelines. For example:

The contrast between the beige and orange is a bit low. The ratio is currently 3.2:1 with f94a0a being the orange, If we switch to CA3C08, then we can bump the ratio to 4.6:1.

I did a quick audit of contrast ratios throughout the theme using the HTML5 Code Sniffer bookmarklet at ​http://squizlabs.github.com/HTML_CodeSniffer/. Note that this checker calculates ratios to 2 decimal places, so the results look slightly different than Aaron's on the same elements -- but my 3.19 is close enough to Aaron's 3.2, and both of them miss the 4.5 mark by a good bit.

Great catch, George -- turns out that the same is true of all Header levels except H3 (which is specifically styled since it's the widget-title for all the default widgets). Adding it to the master list.